Holographic laser scanning system having multiple laser scanning stations for producing a 3-D scanning volume substantially free of spatially and temporally coincident scanning planes

Abstract

A holographic laser scanner of ultra-compact design capable of reading bar and other types of graphical indicia within a large scanning volume using holographic optical elements and visible laser diodes. The holographic optical elements are arranged on the scanning disc in such a manner so that none of the laser scanning planes generated within the 3-D scanning volume of the system are spatially and temporally coincident with any other laser scanning plane within the 3-D scanning volume. This novel feature of the present invention ensures that there is substantially zero cross-talk at the plurality of photodetectors provided within the system, significantly improving the performance of the system.

What is claimed is: 
     
       1. A holographic laser scanning system for producing a 3-D scanning volume substantially free of spatially and temporally coincident laser scanning planes, said holographic laser scanning system comprising: a housing;   a plurality of laser sources disposed within said housing, for producing a plurality of laser beams;   holographic scanning disc disposed within said housing, rotating about an axis of rotation, and having a plurality of holographic optical elements for scanning said plurality of laser beams and producing within a 3-D scanning volume, a plurality of laser scanning planes for scanning a code symbol;   a plurality of photodetectors disposed within said housing, each said photodetector being associated with one said laser source and being capable of detecting laser light reflected off a code symbol scanned by the laser beam produced by said associated laser source;   wherein said plurality of holographic optical elements are physically ordered about said holographic scanning disc so that substantially none of said laser scanning planes within said 3-D scanning volume are spatially and temporally coincident with any other laser scanning plane in order to ensure that there is substantially zero cross-talk at said plurality of photodetectors.   
     
     
       2. The holographic laser scanning system of claim 1, wherein each said laser scanning plane has predefined beam characteristics; and said plurality of laser scanning planes intersect within said 3-D scanning volume and said predefined beam characteristics of said scanning planes cooperate within said 3-D scanning volume so as to produce an omnidirectional laser scanning pattern within said 3-D scanning volume for omnidirectional scanning anywhere therewithin, code symbols having a predetermined bar/space resolution.   
     
     
       3. The holographic laser scanning system of claim 1, wherein said 3-D scanning volume has at least three focal zones, and a depth of field of at least 10 inches. 
     
     
       4. The holographic laser scanning system of claim 1, wherein said 3-D scanning volume is in the shape of a 3-D polygonal shaped object. 
     
     
       5. The holographic laser scanning system of claim 4, wherein said 3-D polygonal shaped object has at least four substantially rectangular shaped side surfaces. 
     
     
       6. The holographic laser scanning system of claim 1, wherein each said laser source comprises a laser diode for producing one said visible laser beam. 
     
     
       7. The holographic laser scanning system of claim 6, wherein said laser diodes are symmetrically arranged about said holographic scanning disc. 
     
     
       8. The holographic laser scanning system of claim 1, wherein each said holographic optical element is a volume hologram. 
     
     
       9. The holographic laser scanning system of claim 8, wherein each said volume hologram is a transmission-type volume hologram. 
     
     
       10. The holographic laser scanning system of claim 1, wherein said plurality of laser sources comprises at least three laser diodes, said plurality of holographic optical elements comprises at least sixteen volume transmission holograms, and said plurality of laser scanning planes comprises at least forty-eight laser scanning planes, none of which are spatially and temporally coincident with any other laser scanning plane, thereby ensuring that there is substantially zero cross-talk at said plurality of said photodetectors.